Certain electrical connectors comprise a dielectric housing containing a plurality of closely spaced electrical contacts or terminals having posts extending outward parallel to each other to be inserted into corresponding through-holes of a printed circuit board. The through-holes are plated with an electrically conductive material so that an electrical connection is formed when the posts of terminals are inserted therethrough. It is desirable that the posts be held tightly in the through-holes, and the through-holes are dimensioned such that after plating thereof the posts must be wedged into the through-holes during insertion. For this purpose the posts are preferably square or rectangular having corners which "bite" into the plating material during insertion. U.S. Pat. No. 4,186,982 discloses additionally forming compliant contact sections along the posts which significantly enhances the mechanical strength of the engagement of the posts in the plated through-holes and their retention therein. Correspondingly, greater force is needed to push such posts into the through-holes.
In a connector having a plurality of such terminals, the force needed to insert all of the terminals into the array of through-holes is usually much greater than that which can economically be manually applied. For instance, if an average of twenty pounds or so per terminal is needed and, for instance, fifty terminals may be contained in the connector, a total force of one thousand pounds is required. The design of the connector housing most commonly is such that all terminals must be inserted simultaneously.
It is preferable for the force to be applied directly to the terminals individually rather than for the force to be applied to the housing, because application of the force to the housing may result in the terminals merely becoming dislodged from their respective cavities in the housing and only being partially inserted if at all into the printed circuit board. Further, it is preferable that the force be applied precisely vertically to push surfaces on the terminals and centered thereon, if applied by individual push pins of the application tooling of the apparatus; that the terminals be securely and precisely held in a vertical alignment normal to the surface of the board throughout the insertion procedure; and also that the board be securely and precisely held horizontally in the apparatus. Insertion tooling having push pins is disclosed in U.S. Pat. No. 4,394,795. Also, a mounting press having insertion tooling for connector application is disclosed in U.S. Pat. No. 4,367,583.
The printed circuit board typically has locating holes formed thereon related accurately to the position of the through-holes; using the locator holes, the board can be positioned in the applicator apparatus on locating pins of a holding fixture. While it is possible to secure the printed circuit board in a position such that the connector to be applied is located accurately beneath the applicator tooling of the apparatus, (when partially inserted on the board), it is common that the location and alignment of the arrays of through-holes of the board can vary from board to board within manufacturing tolerances in an amount substantial enough to frustrate previous attempts at automating the application process, because the push pins of the tooling are not centered on the push surfaces of the terminals precisely enough after the terminals are corrected to a true vertical. Such tolerance problems are accentuated when more than one connector is desired to be applied to a board at the same time.
Also, tolerance problems exist with respect to the vertical dimensions of the connector and board and in the application tooling and the press for which compensation should be provided by the apparatus in some manner.
Each connector housing must be mounted on the printed board such that its bottom or mounting surface is flush with the board surface of within a minute incremental distance therefrom to minimize or prevent debris or dust from entering, therebetween or to prevent accidental shorting by a metal object coming into electrical engagement with exposed portions of the contact terminals. Such precision mounting must be accomplished without applying excessive compressive force on the housing, yet enough must be applied to fully mount the connector. And where a plurality of connectors is to be mounted simultaneously by the same fixed downstroke of a reciprocal press ram having a fixed compression force, each connector may have a slightly different vertical dimension for which individual compensation must be provided by the application tooling.